Warning device for a vehicle

ABSTRACT

A warning device for a vehicle comprises a steering angle detector 10 producing steering angle pulses S 2 , S 3  indicative of the steering angle and the steering direction whenever the variation of the steering angular position exceeds a predetermined angle, a dozing detecting circuit 16 which distinguishes that the driver is in normal condition when excessively frequent steering operations in one direction are performed and distinguishes that the driver is dozing to produce a warning signal when steering operations, each of which does not exceed the predetermined angle in one direction, are repeated at a rate greater than a predetermined frequency, and a warning means 26 for producing visible or audible warning in response to the warning signal, whereby, the warning device can accurately detect dozing of the driver and produce a warning to make the driver wake up.

FIELD OF THE INVENTION

The present invention relates to a warning system for an automotivevehicle and the like. More particularly, the invention relates to awarning system for a vehicle which detects dozing of a vehicle driverand produces a warning in response.

BACKGROUND OF THE INVENTION

If a vehicle driver dozes while driving the vehicle, driving operationsdistinct from operations performed under normal waking conditions willoccur. Therefore, by detecting abnormal driving operations occurringwhen the driver dozes at the wheel, dozing of the driver can bedetected. The dozing of the driver can be thus corrected by warning thedriver when abnormal driving operations are performed.

Therefore, it is an object of the present invention to provide a warningsystem for a vehicle which detects specific driving operations likely tobe performed during dozing of the driver to produce a warning.

SUMMARY OF THE INVENTION

The above-mentioned and other objects are accomplished by a warningsystem for a vehicle according to the present invention, which detectsthe frequency of steering operation within a unit time and produces awarning when the detected steering operation frequency exceeds apredetermined frequency which is preset to a frequency higher than thatperformed during normal driving. Furthermore, according to the presentinvention, if steering operations in the same direction are performed atan excessive frequency, the discrimination that the vehicle driver issteering through a curve will be made to prevent the device fromproducing the warning.

According to the preferred embodiment of the invention, the warningdevice for the vehicle comprises steering angle detecting means fordetecting steering angle and steering direction and for producing asignal representative of detected steering angle and steering direction,a dozing detecting circuit for counting the occurrences of steeringoperations within a predetermined period, for clearing the counted valuewhen a signal indicative of a constant steering direction is producedfor a time duration longer than a predetermined time, and for producinga warning signal when the counted value exceeds a predeterminedthreshold value, a warning means for producing the warning in responseto the warning signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a first embodiment of a warning deviceaccording to the present invention;

FIG. 2 is a plan view showing a steering angle sensor employed by thewarning device of FIG. 1;

FIG. 3 is a section taken along line A--A of FIG. 2;

FIG. 4 is a perspective view of part of the steering angle sensor ofFIG. 2, viewed from an angle revealing the movable contact thereof;

FIG. 5 is a perspective view of part of the steering angle sensor ofFIG. 2, viewed from an angle revealing the upper surface thereof;

FIG. 6 is a plan view of the steering angle sensor rotated towardclockwise direction;

FIG. 7 is a plan view similar to FIG. 6 and showing the steering anglesensor at a neutral position;

FIG. 8 is a plan view similar to FIG. 6 and showing the steering anglesensor rotated counterclockwise;

FIG. 9 is a block diagram of the steering angle pulse generator of FIG.1;

FIG. 10 is a timing chart for the warning device of FIG. 1;

FIG. 11 is a block diagram of the second embodiment of the warningdevice of the present invention;

FIG. 12 is a timing chart for the warning device of FIG. 11;

FIG. 13 is a block diagram of the third embodiment of the warning deviceof the present invention; and

FIG. 14 is a block diagram of the fourth embodiment of the warningdevice of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedhereinafter with reference to the attached drawings. FIG. 1 shows thefirst embodiment of a warning system according to the present invention.The steering angle of the vehicle is detected by a steering angle sensor12. The steering angle sensor produces a steering angle signal S₁representative of the steering angle and steering direction. Thesteering angle signal S₁ is inputted to a steering angle pulsegenerating circuit 14. The steering angle pulse generating circuit 14 inconjunction with the steering angle sensor 12 constitutes a steeringangle detector 10. The steering angle pulse generator 14 producessteering angle pulses S₂ and S₃, respectively representative ofdifferent steering directions, in response to a predetermined steeringangle change. In the preferred embodiment, the steering angle pulsegenerating circuit 14 produces a steering angle pulse S₂ for every 5degrees of counterclockwise steering change and a steering angle pulseS₃ for every 5 degrees of clockwise steering change.

The steering angle pulse generating circuit 14 is connected to a dozingdetecting circuit 16 via leads 18 and 20. The steering angle pulse S₂ isfed to the dozing detecting circuit 16 via the lead 18 and the steeringangle pulse S₃ is fed to the dozing detection circuit via the lead 20.The dozing detecting circuit 16 comprises a warning signal generatingsection 22 and a control section 24 for controlling operation of thewarning signal generating section 22. The warning signal generatingsection 22 counts the steering angle pulses inputted thereto within apredetermined period of time and produces a warning signal S₄ when thecounted value exceeds a predetermined threshold value. The controlsection 24 counts the pulses of either steering angle signal S₂ or S₃sequentially inputted thereto and produces a reset signal S₅ when thecounted value thereof exceeds a predetermined value in order to clearthe counted value of the warning signal generating section 22. Thecontrol section 24 clears its own counted value in response to a pulsefrom the steering angle signal S₃ or S₂ other than the one beingcounted. Therefore, the warning signal generating section 22 produces awarning signal S₄ when steering is performed in opposite directions atmore than a predetermined frequency. The warning means 26 is driven inresponse to the warning signal S₄. The warning means 26 produces anywarning which can awake the driver and may provide, for example, abuzzer, a warning voice, discharge of cold air into the driver's face, adisplay, a lamp and so on just as long as an appropriate device forproducing the selected warning is employed as the warning device.

FIGS. 2 to 9 show the detail of the steering angle detector in the firstembodiment. A first gear 102 is fixed at its center portion to asteering column shaft 104 so as to rotate together with the steeringcolumn shaft 104 and a column tube 106. A second gear 108 engages thefirst gear 102. The second gear 108 is rotatably supported by a shaft110 fixed at its bottom end to the column tube 106. In this embodiment,the gear ratio of the first gear 102 to the second gear 108 ispreferably set at 3 to 1 so that, when the first gear 102 rotates once,the second gear 108 rotates three times. The second gear 108 has a firstmember 112 extending downwards from the bottom of the second gear 108and positioned near the periphery thereof. A second member 114 ofdisc-shaped configuration has a strip-like projection 116 on the uppersurface of second member 114. The lower end of the first member 112 ispositioned in such a way that, when the first member 112 moves inresponse to the rotation of the second gear 108, it can push theprojection 116 together with the second member 114 so that the secondmember 114 will rotate through a predetermined angle. The second member114 has a strip-like movable contact 118 on the lower side thereofadapted to contact one of a pair of a stationary contacts 120 and 122,shown in FIG. 3, when the second member 114 rotates to either of twogiven positions. Those stationary contacts 120 and 122 are attached tothe top of the column tube 106. The second member 114 is biased by acoil spring 124, shown in FIG. 4, so as to be normally held in a neutralposition as shown in FIG. 7, where the movable contact 118 is centeredbetween the stationary contacts 120 and 122. The movable contact 118 isconnected through a lead wire 126 to a power source (not shown). Thestationary contacts 120 and 122 are connected through lead wires 121 and123 to the steering angle pulse generating circuit 14 of FIG. 1.

The operation of the above-mentioned steering angle detector will bedescribed hereafter. When the steering wheel (not shown) rotatesclockwise, the steering column shaft 104 rotates clockwise together withthe first gear 102 whereby the first member 112 rotates counterclockwisetogether with the second gear 108. Thus, the first member 112 therebycomes to contact with the projection 116 of the second member 114 due tothis counterclockwise rotation. Thus, the second member 114 is rotatedclockwise by the pushing force of the first member 112 of the secondgear 108 against the biasing force of the spring 124 so that the movablecontact 118 thereof comes into engagement with the stationary contact120 as shown in FIG. 8. As the second gear 108 rotates furthercounterclockwise, the projection 116 of the second member 114 separatesfrom the first member 112. As a result, the second member 114 rotates toreturn to its neutral position due to the biasing force of the spring124. On the other hand, when the first gear 102 rotatescounterclockwise, the second gear 108 rotates clockwise together withthe first member 112 whereby the first member 112 comes into engagementwith the projection 116 of the second member 114. The clockwise movementof the first member 112 urges the second member 114 to rotatecounterclockwise so that the movable contact 118 of the second member114 comes into contact with the stationary contact 122 as shown in FIG.6. When the second gear 108 rotates further in the same direction, theprojection 116 of the second member 114 separates from the first member112 so that the second member 114 rotates to return to its neutralposition as shown in FIG. 7.

When the movable contact 118 engages either of the stationary contacts120 and 122, a pulse is sent to the steering pulse generating circuit14.

FIG. 9 shows a block diagram that illustrates an example of the steeringangle pulse generating circuit 14. A first counter 126 is connectedthrough the lead wires 121 and 130 to the stationary contact 120 andthrough the lead wires 123, 134 to the contact 122. The second counter136 is also connected to the contacts 120 and 122 via leads 121, 140 and123, 138, respectively, and counts the number of clockwise rotations ofthe first member 112 upon receipt of signals from the lead wire 138.When the steering wheel begins to rotate in the opposite direction thesecond counter 136 is reset upon receipt of a signal from the lead wire140. The first counter 126 counts the number of rotations of the firstmember 112 upon receipt of signals from the lead wire 130. When thesteering wheel begins to rotate in the other direction, the firstcounter 126 is reset upon receipt of a signal from lead wire 134.

The first and second counters 126 and 136 produce steering angle pulsesignals S₂ and S₃ respectively when the counted value reaches apredetermined value corresponding to a 5 degree change in steeringangle.

Next, details of the dozing detecting circuit 16 will be described withreference to FIGS. 1 and 10. The steering angle pulses S₂ and S₃produced by the steering angle pulse generating circuit 14 are inputtedto an OR gate 162 of the dozing detecting circuit 16 via lead wires 20and 18. The OR gate 162 is responsive to either steering angle pulse S₂and S₃ to turn ON to produce an output S₆. The output S₆ of the OR gate162 is inputted to a monostable multivibrator 221 of the warning signalgenerating section 22. The monostable multivibrator 221 is responsive tothe output S₆ of the OR gate 162 to turn on for a predetermined period,for example, 5 sec., to produce an output S₇. The output S₇ of themonostable multivibrator 221 is fed to a differentiation circuit 222.The differentiation circuit 222 detects the rising edge of themonostable multivibrator output S₇ to produce an output pulse S₈.Additionally, the output S₇ of the monostable multivibrator 221 isinverted by an inverter 223 and then inputted to a differentiationcircuit 224. The differentiation circuit 224 thus detects the trailingedge of the monostable multivibrator output S₇ to produce an outputpulse S₉.

A timer 225 is responsive to the differentiation circuit output S₈ tostart measuring time and produces an output S₁₁ for a predeterminedperiod, e.g., 15 sec., after receiving the pulse S₈. The output S₉ ofthe differentiation circuit 224 serves as reset signal for the timer225.

The differentiation circuit 222 is connected to the set input S of aflip-flop 227 to set the latter with the output S₈. The reset input R ofthe flip-flop 227 is connected to an OR gate 226. The OR gate 226produces an output S₁₀ in response to pulses from either thedifferentiation circuit output S₉ or timer output S₁₁. The output S₁₀ ofthe OR gate 226 serves as reset signal for the flip-flop 227. Theflip-flop 227 produces a high-level output S₁₂ while it is in the setstate.

The output terminal of the flip-flop 227 is connected to one of theinput terminals of each of two AND gates 241 and 242 of the controlsection 24 which controls the warning signal generating section 22. Theother input terminals of the AND gates 241 and 242 are respectivelyconnected to the leads 18 and 20 of the steering angle pulse generatingcircuit 14. The AND gates 241 and 242 are responsive to the steeringangle pulses S₂ and S₃ to produce outputs S₁₃ and S₁₄ respectively,under the condition that the output S₁₂ of the flip-flop 227 is high. Acounter 245 is connected to the AND gate 241 to count the pulses of ANDgate output S₁₃ produced in response to the steering angle pulse S₂. Acounter 246 is connected to the AND gate 242 to count the pulses of theAND gate output S₁₄ produced in response to the steering angle pulse S₃.The counters 245 and 246 are both connected to an OR gate 226 of thewarning signal generating section 22 via respective OR gates 243 and244. The OR gate 243 is also connected to the output terminal of the ANDgate 242. The OR gate 243 produces an output S₁₅ in response to eitherthe output S₁₀ of the OR gate 226 or the output S₁₃ of the AND gate 242.The output S₁₅ of the OR gate 243 serves as a reset signal for thecounter 245 to clear the counter value. The OR gate 244 is connected tothe output terminal of the AND gate 241. The OR gate 244 produces anoutput S₁₆ in response to either the output S₁₀ of the OR gate 226 orthe output S₁₃ of the AND gate 241. The output S₁₆ of the OR gate 244 isinputted to the counter 246 to clear the counter value thereof. Thecounters 245 and 246 produce respective outputs S₁₇ and S₁₈ when theircounter values reach predetermined values.

The output of the flip-flop 227 is inputted to the AND gate 164. The ANDgate 164 is responsive to the output S₆ of the OR gate 162 under thecondition that the output S₁₂ is high, to produce an output S₁₉. Theoutput S₁₉ of the AND gate 164 is inputted to the counter 168. The resetterminal of the counter 168 is connected to the output terminal of theOR gate 166. One of the input terminals of the OR gate 166 is connectedto the output terminal of the OR gate 226 and the other input terminalthereof is connected to the output terminal of the OR gate 247. The ORgate 247 is turned on to produce an output S₂₀ in response to either ofoutputs S₁₇ or S₁₈ of the counters 245 and 246 respectively. The OR gate166 produces a reset signal S₅ in response to either the output S₁₀ ofthe OR gate 226 or the output S₂₀ of the OR gate 247. The counter 168 isresponsive to the reset signal S₅ to clear the counter value.

The counter 168 produces a warning signal S₄ to be fed to the warningmeans 26 of FIG. 1 when the counter value thereof reaches apredetermined value. The counter 168 clears its counter value at thesame time it produces the warning signal S₄.

In the above construction, the operation will be described withreference to the timing chart of FIG. 10. When right hand steering pulseS₂ or left hand steering pulse S₃ is outputted from the steering anglepulse generator 14, the OR gate 162 outputs the pulse signal S₆. Themonostable multivibrator 221 is responsive to pulses of the signal S₆ toturn on for the predetermined period, for example, 5 sec. If the nextpulse signal S₆ is inputted during the period in which the monostablemultivibrator is kept ON, the period is prolonged. Therefore, absence ofthe output of the monostable multivibrator 221 indicates that the pulsesignal S₆ has not been produced for at least 5 sec. The rising edge ofthe output of the monostable multivibrator 221 is detected by thedifferentiation circuit 222. The differentiation circuit 222 producesthe output S₈ each time it detects a rising edge of the monostablemultivibrator output. In addition, the output of the monostablemultivibrator 221 is inputted to the differentiation circuit 224 via theinverter 223. The differentiation circuit 224 detects the falling edgeof the output S₇ to produce the output S₉. The flip-flop 227 is set bythe output S₈ of the differentiation circuit 222 to output a high-levelsignal S₁₂. At the same time, the timer 225 turns ON in response to theoutput S₈ of the differentiation circuit 222 and outputs the signal S₁₁when a preset time period, e.g., 15 sec. expires. The flip-flop 227 isreset by the output S₁₀ of the OR gate 226. The flip-flop 227 feeds asignal having value "1" to the AND gate 164 until it is reset. Thecounter 168 counts the output pulses S₁₉ of the AND gate 164 to countthe occurrence of the steering angle pulses S₂ and S.sub. 3. The counter168 produces the warning signal S₄ when the counter value reaches apredetermined value, e.g., 7. On the other hand, while the flip-flop 227is maintained at ON position, the AND gates 241 and 242 conduct theright-hand and left-hand steering angle pulses S₂ and S₃. The counters245 and 246 count respective steering angle pulses S₂ and S₃. Respectivecounters 245 and 246 operate to feed the reset signal S₅ to the counter168 via the OR gate 247 and the OR gate 166 when either counter valuereaches the predetermined value, e.g., 4. In the foregoing embodiment,when the steering operation is in a constant direction, for example,driving through a curve, the counter value of the counter 168 is resetby the reset signal S₅ and thus the warning signal will not be produced.In other words, when alternating-direction steering operations whichproduce less than 4 sequential right-hand or left-hand steering anglepulses S₂ and S₃, are effected and when the counted value of thesteering angle pulses S₂ and S₃ reaches 7, the warning means 26 producesa warning.

Referring to FIG. 11, there is illustrated the second embodiment of thepresent invention, in which the warning means is not instantlyresponsive to the warning signal S₁₂. In this embodiment, the warningsignal S₁₂ is held for a predetermined time period and the warning meansproduces the warning after expiration of the foregoing time period andonly if the signal indicative of steering through a curve is notinputted during that predetermined period. Elements analogous to thoseof the foregoing first embodiment are represented by the same referencenumerals and thus further explanation therefor is neglected in thedescription given hereinbelow. In addition to the first embodiment,there are provided a flip-flop 302 which can be set by a first warningsignal S₂₁ and reset by the output of the OR gate 166, a monostablemultivibrator 304 detecting the falling edge of the output of theflip-flop and turning on for a predetermined time period after detectingthe falling edge of the flip-flop output, and an AND gate 306, receivinginputs from the monostable multivibrator 304 and the OR gate 226, whichproduces an output to be fed to the warning means 26.

In the above construction, the function will be described with referenceto the timing chart of FIG. 12. When the first warning signal S₂₁ isoutputted from the counter 168, the flip-flop 302 is turned on toproduce a signal S₂₂. At the time the level of the flip-flop 302 outputS₂₂ drops in response to the output S₅ of the OR gate 166, which isindicative of expiration of counting time, the monostable multivibrator304 is turned ON for the predetermined time period to produce an outputS₂₃. Therefore, when the reset signal S₂ is outputted from the controlsignal 24 during the steering pulse counting period, the AND gate 306 isprevented from producing the second warning signal S₄. Thus, only whenthe reset signal S₅ is not produced will the warning signal S₄ be fed tothe warning means 26.

FIG. 13 shows the third embodiment of the present invention. In thisembodiment, a vehicle speed sensor 402, for producing an output "1" whenthe vehicle speed is higher than a preset speed, and AND gates 404 and406, permitting the steering angle pulses S₂ and S₃ from the steeringangle pulse generator to pass therethrough under the condition that theoutput of the vehicle speed sensor 402 is high, are added to theforegoing first embodiment. Thus, the warning will not be created whiledriving through a city or at a relatively low speed.

FIG. 14 shows the fourth embodiment of the present invention. The fourthembodiment comprises a first warning section 502 which receives thewarning signal S₂₄ directly, a time setting circuit 504 to be turned onfor a predetermined time period in response to the warning signal S₂₄,an AND gate 506 permitting the warning signal S₄ to pass therethroughonly when the time setting circuit 504 is in the ON condition, a counter508 for counting the pulses from the AND gate 506 to produce a secondwarning signal S₂₅ and resetting the counter value thereof when thecounter value reaches a predetermined value and a second warning section510 respective to the second warning signal S₂₅ to produce a warning, inaddition to the construction of the foregoing first embodiment. Thefirst warning section 502 produces warning via a visible display,lighting a lamp or the like as a gentle warning. When the dozingdetecting circuit 16 sequentially and continuously produces the warningsignal S₂₅, the second warning section 510 produces a rather strongwarning such as a buzzer, a warning voice, discharging cold air or thelike.

As described hereabove, according to the present invention, whenvariation of the steering angle position from a certain standardsteering angle continues in the same direction at a rate exceeding apredetermined frequency, indication is given that the vehicle is beingsteered through a curve in order to inhibit counting of the steeringfrequency. If the steering operations in alternating directions exceedthe predetermined frequency, the warning is produced. This ensuresdetection of drowsiness of the driver and thus can effectively preventthe driver from falling asleep.

We claim:
 1. A warning device for a vehicle comprising:steering angledetecting means for detecting steering angle and direction and forproducing signals representative of the detected steering angle anddirection; dozing detecting means responsive to said signals formeasuring steering frequency within a predetermined time period and forproducing a warning signal and clearing said measured frequency whensaid measured frequency exceeds a threshold value; and a warning meansfor producing a warning in response to said warning signal.
 2. A warningdevice for a vehicle comprising:a steering angle detecting means forproducing pulse signals whenever variation of the steering angularposition from a predetermined standard position exceeds a predeterminedangle; a dozing detecting means includinga warning signal generatingmeans for counting pulses of said pulse signals and producing a warningsignal when the counted value reaches a threshold value within apredetermined time period, and a control means for counting pulses ofsaid pulse signals representing the steering angle variation in only onedirection to produce a reset signal for clearing the counted value ofsaid warning signal generating means when the value counted by saidcontrol section reaches a predetermined value; and a warning means forproducing a warning in response to the warning signal.
 3. A device asset forth in claim 2, wherein said dozing detecting means furthercomprises a timer means starting simultaneously with the countingoperation of said warning signal generating means for measuring time andproducing an output when a given period of time is expired; and countermeans for counting the pulses of said pulse signals and connected forbeing cleared in response to said output of the timer means.
 4. A deviceas set forth in claim 3, wherein said control means comprises first andsecond counters which respectively count the pulses of said signalsrepresentative of respective opposite steering directions, each of saidfirst and second counters responsive to the output of the timer meansand the signal of the other of said first and second counters of thecontrol means to clear the counter value thereof, said counters of thecontrol means also being cleared in response to a reset signal producedwhen the counter value of the counters of the control means reaches apredetermined value.
 5. A device as set forth in claim 4, wherein saidcounter means is connected to be reset by signals from said first orsecond counters and is further connected to provide the warning signalto the warning means via a delay circuit means for providing the warningsignal after a predetermined delay time expires, and said delay circuitmeans further operative for cancelling the warning signal when the resetsignal fed from the control means is inputted thereto within thepredetermined delay time.
 6. A device as set forth in claim 4, whichfurther comprises a vehicle speed sensor means for detecting vehiclespeed and producing an output when the detected vehicle speed is higherthan a given speed and gate means for permitting the signals of thesteering angle detecting means to be inputted to the dozing detectingmeans when the output of the vehicle speed sensor is produced.
 7. Adevice as set forth in claim 4, wherein said warning means comprises afirst warning means directly connected with the dozing detecting meansto immediately respond to the warning signal to produce a first warningand a second warning means connected to the dozing detecting means via adelay circuit for producing a second warning after expiration of apreset delay time.
 8. A method for waking the driver of a vehicle fromdozing comprising the steps of:detecting steering angle and direction tomeasure steering frequency; comparing the measured frequency with apredetermined threshold value to produce a warning for waking the driverwhen the measured frequency value is equal to or more than the thresholdvalue.
 9. A method as set forth in claim 8, comprising the further stepof clearing said measured frequency value when the frequency ofsequential steering operations in a single direction exceeds apredetermined value.
 10. A method as set forth in claim 9, comprisingthe further steps of producing said warning with a predetermined timedelay after the measured value exceeds the threshold value, andinhibiting production of the warning if sequential steering operationsin a single direction exceed a predetermined number within thepredetermined time delay and thus the measured frequency value iscleared.
 11. A method as set forth in any one of claims 8, 9 or 10,which further comprises the step of measuring vehicle speed andeffecting measurement of the steering frequency when the measuredvehicle speed is higher than a predetermined speed.
 12. A method as setforth in claim 8, 9 or 10, comprising the further steps of producing afirst warning to wake the driver when the measured frequency valueexceeds said threshold value and producing a second warning when apredetermined delay time expires and the frequency value has not beencleared.
 13. A warning device for a dozing vehicle drivercomprising:steering angle detecting means for detecting steering angularvariation and producing a first steering angle indicative signalwhenever the steering angular variation in one direction exceeds apredetermined angle and a second steering angle indicative signalwhenever the steering angular variation in the other direction exceeds apredetermined angle; dozing detecting means, responsive to said firstand second steering angle indicative signals, for detecting a number ofoccurrences of said first and second steering angle indicative signalswithin a given period of time to produce a warning signal when thenumber of detected occurrences equals or exceeds a predeterminedthreshold; and a warning means for producing a warning in response tosaid warning signal.
 14. A warning device for a dozing vehicle drivercomprising:a steering angle detecting means for detecting steeringangular variation and producing a pulse form first steering angleindicative signal in response to variation of steering angular positionin one direction exceeding a predetermined angle and a pulse form secondsteering angle indicative signal in response to variation of steeringangular position in the other direction exceeding a predetermined angle;dozing detecting means, responsive to said first and second steeringangle indicative signals, for counting said first and second signals toproduce a warning signal when the counted value reaches a predeterminedthreshold, said dozing detecting means measuring a period of time inwhich said first and second steering angle indicative signals arecounted, to clear the counted value when the measured period of timeequals or exceeds a given time threshold; and warning means forproducing a warning in response to said warning signal.
 15. A warningdevice for a dozing vehicle driver, comprising:steering angle detectionmeans detective of frequency of oscillation of a steering wheel forproducing a first steering angle indicative signal in pulse form at eachtime the variation of steering angular position in one direction exceedsa predetermined value and a second steering angle indicative signal inpulse form at each time the variation of steering angular position inthe other direction exceeds said predetermined value; dozing detectingmeans for mounting said first and second steering angle indicativesignals to produce a warning signal when the counted value reaches apredetermined threshold within a given period of time; reset signalgenerator means for counting one of said first and second steering angleindicative signals to produce a reset signal for resetting said dozingdetecting means when the counted number of said one of said signalsreaches a given value; and a warning means for producing a warning inresponse to said warning signal.
 16. A device as set forth in claim 13,which further comprises a reset signal generator means associated withsaid dozing detecting means for detecting occurrence of one of saidfirst and second steering angle indicative signals to produce a resetsignal for resetting said dozing detecting means when the detectedoccurrences of said one of said signals reaches a given value, saiddozing detecting means including a counter means for counting said firstand second steering angle indicative signals, said counter meansconnected for clearing the counter value thereof when said given periodof time expires.
 17. A device as set forth in claim 14, which furthercomprises a reset signal generator means associated with said dozingdetecting means for counting one of said first and second steering angleindicative signals to produce a reset signal for resetting said dozingdetecting means when the counted number of said one of said signalsreaches a given value,said dozing detecting means including a counterfor counting said first and second steering angle indicative signals anda timer for measuring a period of time to produce a timer output whensaid given time threshold expires.
 18. A device as set forth in claim15, wherein said dozing detecting means includes a timer means connectedfor starting simultaneously with the counting operation of said firstand second steering angle indicative signals for measuring time andproducing a timer output when a given period of time expires.
 19. Awarning device for preventing a vehicle driver from dozing at the wheel,comprising:a first detector detecting variation of steering angularposition and producing a first pulse form signal indicative of steeringangular variation in one direction and a second pulse form signalindicative of steering angular variation in the other direction; asecond detector counting said first and second signals occurring withina given period of time to detect extraordinarily high frequency ofsteering angular variations exceeding a given threshold and producing awarning signal when the counted value exceeds a predetermined threshold;a third detector counting one of said first and second signals fordetecting a driving condition of passing through a curved road bydetecting continuous occurrence of one of said first and second signals,and producing a reset signal for resetting said counted value in saidsecond detector when the counted value of said third detector reaches agiven reset threshold; and a warning device responsive to said warningsignal to produce a warning.
 20. A device as set forth in claim 19,wherein said third detector comprises a first counter for counting saidfirst signal and producing said reset signal when the first countervalue reaches said given value, and a second counter counting saidsecond signal and producing said reset signal when the second countervalue reaches said given value, said first counter responsive to saidsecond signal to clear said first counter value and said second counterresponsive to said first signal to clear said second counter value. 21.A device as set forth in claim 20, which further comprises a timer formeasuring said given period of time to produce a timer signal forclearing the counted value in said second detector when said givenperiod of time expires.
 22. A device as set forth in claim 21, whereinsaid first and second counters in said third detector are associatedwith said timer to clear said first and second counter values inresponse to said timer signal.
 23. A method for warning a vehicle driverdozing at the wheel, comprising the steps of:detecting angular variationof steering to produce a first signal evertime the angular variation ofthe steering in one direction exceeds a predetermined angle and toproduce a second signal everytime the angular variation in the otherdirection exceeds said predetermined angle; counting said first andsecond signals to produce a warning when the counted value reaches apredetermined warning threshold; measuring a period of time running fromstarting of said counting of said first and second signals to clear saidcounted value when measured period reaches a given time threshold.
 24. Amethod for preventing a vehicle driver from dozing, comprising the stepsof:detecting angular variation of steering to produce a first signal inpulse form at each predetermined angle of angular variation of steeringin one direction and a second signal in pulse form at each predeterminedangle to angular variation of steering in the other direction; countingsaid first and second signals to produce a warning when the countedvalue reaches a predetermined warning threshold; detecting continuousoccurrence of one of said first and second signals exceeding apredetermined reset threshold to produce a reset signal for clearingsaid counted value; and measuring a period of time running from startingof said counting operation of said first and second signals to clearsaid counted value when the measured period exceeds a given timethreshold.
 25. A method as set forth in claim 23, which furthercomprises the step of detecting continuous occurrences of one of saidfirst and second signals in excess of a predetermined reset threshold toproduce a reset signal for clearing said counted value.
 26. A method asset forth in claim 24 or 25, which further comprises a step of providinga time delay after said counted value reaches said warning threshold,disabling production of said warning when continuous occurrence of oneof said first and second signals exceeding said reset threshold isdetected within said time delay, and clearing said counted value at thesame time of disabling production of said warning.
 27. A method as setforth in claim 24 or 25, which further comprises a step of producing afirst warning when said counted value exceeds said warning threshold andproducing a second warning when a predetermined time delay expires andsaid counted value is not cleared.
 28. A device as set forth in claim 1,wherein said dozing detecting means further comprises a timer meansstarting simultaneously with a counting operation of said warning signalgenerating means for measuring time and producing an output when a givenperiod of time is expired; and counter means for counting pulses of saidsignals representative of the detected steering angle and direction andconnected for being cleared in response to said output of the timer. 29.A device as set forth in claim 28, further comprising a control meansfor counting said signals representative of the detected steering angleand direction, wherein said control means comprises first and secondcounters which respectively count the pulses of said signalsrepresentative of respective opposite steering directions, each of saidfirst and second counters responsive to the output of the timer meansand the signal counted by the other of said first and second counters ofthe control means to clear the counter value thereof, said counters ofthe control section also being cleared in response to a reset signalproduced when the counter value of the counters of the control sectionreaches a predetermined value.
 30. A warning device for a vehiclecomprising:steering angle detecting means for detecting steering angleand direction and for producing signals representative of the detectedsteering angle and direction; dozing detecting means responsive to saidsignals for measuring steering frequency within a predetermined timeperiod and responsive to measurement of a predetermined steeringfrequency within said predetermined time period and for producing awarning of driver drowsiness; and means for disabling said dozingdetecting means in response to detection of a curved road drivingcondition by detection of a sequence of one of said steering signalsrepresentative of a continuous steering operation in one direction.